[btilly]

Reference needed supporting your claim that it was so widely understood.

My strong impression is that it wasn't until James Gleick published Chaos: Making a New Science in the 1980s that there was a popular treatment available to the lay public. And that book lays out many examples from the early 1960s at people like Edward Lorenz and Yoshisuke Ueda being surprised at extreme sensitivity to initial conditions, and having their discoveries met by doubt and disbelief. Which indicates pre-1960, only a fairly niche audience was strongly aware of chaos theory among either the lay public or scientists.

[Gordonjcp]

Okay, have you heard of Henri Poincaré? Because he studied chaos in the 1880s, and anyone with a high-school level grasp of mathematics would know that.

Hinged pendulums which exhibit chaotic behaviour have been a popular demonstration for about 100 years.

Just because the first pop-sci glossy coffee table book to mention chaos wasn't published until the 1980s, it doesn't mean that anyone who studied maths or physics - particularly at a level that would allow them to teach at a university - would not have even heard of chaos theory.

[btilly]

Given that I pointed out Poincaré in https://news.ycombinator.com/item?id=33285644 I clearly have heard of him.

The double pendulum actually goes back further. It was studied in the 1700s. But what could be done with them was limited until computer simulations were available - in the 1960s. The same time that chaos as a subject became a thing.

And your claim that chaos was something that anyone with a high-school grasp of mathematics would have known about in the 1940s is supported on nothing more than your say-so. And directly contradicts multiple reports of working scientists in the 1960s. For example from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3202497/ you find:

Lorenz considered, as did many mathematicians of his time, that a small variation at the start of a calculation would Induce a small difference In the result, of the order of magnitude of the initial variation. This was obviously not the case, and all scientists are now familiar with this fact.

In other words people with PhD in directly relevant fields in the 1960s actually were ignorant of basic facts about chaos theory that are now known to every high school student. Even the phrase we all have heard to capture it, namely "the butterfly effect", dates from the 1970s.

And with that, I'm done. You're providing assertions that run counter to my citations, and are refusing to accept information that I cited about what was and was not general knowledge. There is no point in continuing.